Comparative proteomic analysis of oral squamous cell carcinoma and adjacent non-tumour tissue from Thailand

The study was aimed at analysing and identifying the proteins that are differentially expressed in oral squamous cell carcinoma (OSCC) compared to adjacent non-tumour tissue.

Two-dimensional (2D) sodium dodecyl sulphate-polyacrylamide gel electrophoresis accompanied by mass spectrometry (matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry and liquid chromatography-tandem mass spectrometry) was used to analyse and identify the differentially expressed proteins in 10 pairs of tumours and adjacent non-tumour tissues from five cases of early-stage and five cases of late-stage OSCC. The statistical differences of the protein spots were analysed by the Wilcoxon signed-rank test. A validation study using immunohistochemistry and quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) was performed.

A total of 68 proteins (63 up-regulated, five down-regulated) were differentially expressed in early-stage disease, and 39 proteins (37 up-regulated, two down-regulated) were significantly altered in late-stage disease. Among these, 14 proteins were altered in both groups. A total of 44 proteins were identified, including heat shock proteins (HSPs: Hsp90, HSPA5 and HSPA8), keratins (K1, K6A and K17), tubulin, cofilin 1, 14-3-3σ and metabolic enzymes. These proteins are involved in various cellular processes essential for cell growth, survival and cell migration. The validation study on α-tubulin and 14-3-3σ using immunohistochemistry and KIAA1199 expression using real-time RT-PCR confirmed the results in proteomics analysis.

The study identified many proteins, both known and unknown, for cancer cell processes. At least two proteins, KIAA1199 and Horf6, are novel for oral cancer.